JP6998504B2 - Insulation material and equipment using the insulation material - Google Patents

Description

The present invention relates to a heat insulating material and a device using the heat insulating material. In particular, the present invention relates to a flame-retardant heat insulating material and equipment using the heat insulating material.

In recent years, in the fields of automobiles and industrial equipment, it is necessary to establish heat flow control, safety, and fire prevention in a limited narrow space. For this reason, there is a demand for an unprecedented high-performance heat insulating material that has both excellent heat insulating properties that can effectively block heat even if it is thin, flame retardancy, and heat resistance.

Therefore, flame-retardant polyurethane to which a flame retardant is added has been developed. As the flame retardant polyurethane, a general brominated flame retardant or the like is used as a flame retardant for a resin. These are based on a mechanism in which the surface is carbonized during combustion to prevent the progress of combustion. However, since the upper limit temperature for use is around 100 ° C., there is a problem that it cannot be used in a high temperature range of 100 ° C. or higher (Patent Document 1). Further, since it is a foam, there is a problem that it is difficult to process it thinly to a thickness smaller than the foam diameter.

On the other hand, a heat insulating material called silica airgel is known. Silica lyca airgel has a network structure in which silica particles on the order of several tens of nm are connected by point contact, and the average pore diameter is 68 nm or less in the mean free path of air. Therefore, it is lower than the thermal conductivity of static air.

Japanese Patent No. 5785159

However, silica airgel may have a problem in flame retardancy and heat resistance because the organic modifying group may be thermally decomposed to generate a flammable gas in a high temperature environment.

Therefore, the subject of the present application is to provide a heat insulating material having both high heat insulating property that can effectively block heat even in a narrow space and flame retardancy that can prevent burning, and a device using the heat insulating material. be.

In order to solve the above problems, a heat insulating material containing a silica xerogel, a carbon material, and a non-woven fabric fiber holding the silica xerogel and the carbon material is used.

Further, the silica xerogel and the carbon material are used without containing the silica xerogel, the carbon material, the composite layer of the three components composed of the non-woven fabric fiber, and the non-woven fabric fiber arranged on one surface of the composite layer of the three components. The heat insulating material containing a two-component composite layer containing the silica xerogel and a single layer containing silica xerogel arranged on the other surface of the three-component composite layer is used.

Further, a device in which the above-mentioned heat insulating material is arranged as a part of a heat-retaining or cold-retaining structure or between a heat-generating component and a housing is used.

According to the heat insulating material of the present invention, since the thermal conductivity is lower than that of the conventional heat insulating material, a sufficient heat insulating effect can be exhibited even in a narrow space in electronic equipment, in-vehicle equipment, and industrial equipment, and from heat generating parts to a housing. Heat transfer can be effectively reduced. Further, since the heat insulating material of the present invention has flame retardancy, in addition to the heat insulating effect, it also has a burning preventing effect of preventing burning in the event of thermal runaway or ignition.

(A)-(b) Cross-sectional view of the flame-retardant heat insulating material of the embodiment The figure which shows the two-component composite layer of silica xerogel and carbon material of an embodiment. The figure which shows the three-component composite layer of the silica xerogel of an embodiment, a carbon material, and a non-woven fabric fiber. The figure which shows the carbon material of (a)-(f) embodiment The figure of the manufacturing method of the flame-retardant heat insulating material of embodiment The figure which shows the process of impregnating the non-woven fabric fiber with the carbon material dispersion raw material of the embodiment (a)-(b). The figure which shows the detailed condition and evaluation result of an Example and a comparative example. The figure of the SEM image of the cross section of the heat insulating material produced in Example 1 and Comparative Example 1.

Next, the present embodiment will be described with reference to one preferred embodiment of the invention.
<Example of structure of heat insulating material 108>
The heat insulating material 108 of the embodiment is shown in the cross-sectional views of FIGS. 1 (a) and 1 (b).

FIG. 1A is composed of a three-component composite layer 103, a two-component composite layer 102, and a one-component single layer 101.

The three-component composite layer 103 is composed of silica xerogel 115, a carbon material 114, and a non-woven fabric fiber 116.

The two-component composite layer 102 does not contain the non-woven fabric fiber 116, is composed of silica xerogel 115 and a carbon material 114, and is laminated on the three-component composite layer 103.

The one-component single layer 101 is composed of the one-component single layer 101 made of silica xerogel 115.

The silica xerogel 115, carbon material 114, and non-woven fabric fiber of each layer are the same. It is also possible to use different types for each layer.

The role of each layer will be explained.

The three-component composite layer 103 is the main layer of the heat insulating material 108 and is the thickest of the three layers. The three-component composite layer 103 is a layer in which silica xerogel 115 is a main component and determines the heat insulating performance of the heat insulating material 108. The carbon material, which is one of the constituent elements of the three-component composite layer 103, contributes to flame retardancy, and the non-woven fabric fiber 116 functions as a support for making the heat insulating material 108 a self-supporting structure. ..

The two-component composite layer 102 is a layer that determines the flame retardant performance of the heat insulating material 108. The two-component composite layer 102 is thinner than the three-component composite layer 103. However, the carbon material 114, which is a component of the two-component composite layer 102, is present at a higher concentration than the carbon material 114 of the three-component composite layer 103. Therefore, it reacts with O ₂ in the atmosphere to generate more CO ₂ , which contributes to flame retardancy by diluting the combustible gas.

The one-component single layer 101 is made of silica xerogel 115 and is thinner than the three-component composite layer 103, but ensures the smoothness of the surface of the heat insulating material 108. If the single layer 101 of one component is not smooth, the contact thermal resistance becomes large, which affects the heat insulating performance of the heat insulating material 108. The single layer 101 of one component is for ensuring the smoothness of the surface of the heat insulating material 108.

On the other hand, FIG. 1B is a heat insulating material 108 having a three-layer structure in which a two-component composite layer 102 sandwiches a three-component composite layer 103.

In FIG. 1 (b), since the two-component composite layer 102 is present on both sides, high-concentration CO ₂ is emitted from both sides even when flames are contacted on both the front and back surfaces of the heat insulating material 108. Occur. Therefore, the flame retardant effect can be effectively exhibited.

In FIG. 1A, the two-component composite layer 102 is present on only one side. If it is assumed that the flame will come into contact with only one side in advance, the structure shown in FIG. 1 (a) is preferable.

Tables 1 and 2 show the respective components of FIGS. 1 (a) and 1 (b).

In these structures, the filling rate of the silica xerogel 115 in the three-component composite layer 103 can be increased to ensure heat insulating properties.

<Distribution of carbon>
The concentration of the carbon material 114 is different between the two-component composite layer 102, the one-component single layer 101, and the three-component composite layer 103. The two-component composite layer 102 has the highest concentration of the carbon material 114, followed by the three-component composite layer 103 having the carbon material 114 concentration. In principle, the single layer 101 of one component does not contain the carbon material 114.

Further, it is more preferable to change the concentration of the carbon material 114 in the thickness direction also inside the three-component composite layer 103. That is, it is preferable that the concentration gradient is in the vertical direction, with the high concentration in the upper surface direction and the low concentration in the lower surface direction. The upper surface is a surface where the heat insulating material 108 comes into contact with the flame.

When the high-concentration carbon material 114 is uniformly dispersed, the carbon particles are connected along the thickness direction and a heat conduction path is formed, so that the heat conductivity may increase. In this case, the heat insulating property of the heat insulating material 108 is deteriorated, which is not good.

Further, the carbon material 114 located inside the heat insulating material 108 does not contribute to the generation of carbon dioxide.

Therefore, from the viewpoint of achieving both heat insulating properties (thermal conductivity) and flame retardancy, it is preferable to disperse them unevenly at a high concentration on one side rather than uniformly dispersing them.

<Thermal conductivity>
The thermal conductivity of the non-woven fabric fiber is 0.030 to 0.060 W / mK. The thermal conductivity of the composite of silica xerogel 115 and carbon material 114 is 0.010 to 0.015 W / mK. As a result, the thermal conductivity of the heat insulating material 108 is 0.014 to 0.024 W / mK.

<Conventional heat insulating material>
The conventional heat insulating material composed of the silica xerogel 115 and the non-woven fabric fiber 116 has a structure of only a composite layer of two components of the silica xerogel 115 and the non-woven fabric fiber 116. Cracks are likely to occur.

The surface of the silica particles constituting the silica xerogel 115 is organically modified and exhibits hydrophobicity. However, when heated at a high temperature of 300 ° C. or higher, this organic modifying group is thermally decomposed, and trimethylsilanol and the like are desorbed in large quantities as a flammable gas.

Since the conventional heat insulating material does not contain the carbon material 114, this flammable gas may act as a combustion improver. For example, in glass paper made of C glass, the base material itself does not burn. However, when silica xerogel 115 (800 m ² / g or more) having a large specific surface area is compounded with this glass paper, a large amount of flammable gas generated from silica xerogel or 115 ignites, and the glass paper made of C glass burns. There are cases where it will be done. C glass has lower heat resistance than E glass, and although it depends on the basis weight, it shrinks and deforms when heated to 750 ° C. or higher.

<Structure of two-component composite layer 102>
FIG. 2 shows the fine structure of the two-component composite layer 102.

The silica xerogel 115 is a porous structure in which silica secondary particles 112 generated by agglomeration of silica primary particles 111 are connected by point contact and have pores 113 on the order of several tens of nm. The carbon material 114 is incorporated into the three-dimensional network of silica xerogel 115. The carbon material 114 may be connected to the silica primary particles 111 or the silica secondary particles 112 by a covalent bond or may be connected by an intramolecular force.

<Structure of composite layer 103 of three components>
FIG. 3 is a perspective view of a three-component composite layer 103 composed of silica xerogel 115, nonwoven fabric fiber 116, and carbon material 114. As shown in FIG. 3, in the three-component composite layer 103, the carbon material 114 is adsorbed and exists on the surface of the non-woven fabric fiber 116 by electrostatic interaction. It contributes to flame retardancy by reacting with O ₂ in the atmosphere to generate CO ₂ in a flame contact or in a high temperature range of 300 ° C or higher. That is, the carbon material 114 contributes as a flame retardant.

<Carbon material 114>
The carbon material 114 used in the present embodiment is a carbon material 114 containing at least one kind of condensed ring having aromaticity, and reacts with O ₂ in the atmosphere at a high temperature of 300 ° C. or higher to generate CO ₂ . Carbon material 114. The requirements for the carbon material 114 that generates CO ₂ at 300 ° C or higher are that no melting, thermal decomposition, or sublimation occurs during the heating process up to 300 ° C (thermal stability), and that it reacts with O ₂ in the atmosphere. It is easy to have sp carbon (triple bond) and sp2 carbon (double bond). The aromatic fused ring compound is preferable because it is a carbon material 114 that satisfies these requirements.

4 (a) to 4 (f) show an example of the structure of the carbon material 114 that can be used. Fullerene 118 in FIG. 4 (a), graphene 119 in FIG. 4 (b), carbon nanotube 120 in FIG. 4 (c), conductive polymer 121 (polypyrrole, polyaniline, polythiophene, polyacetylene, etc.) in FIG. 4 (d), The polyacene 122 (n = 1 anthracene, n = 2 naphthalcene, n = 3 pentacene, etc.) of FIG. 4 (e) and the carbon black 123 of FIG. 4 (f) can be used.

The type of carbon material 114 is not limited, but from the viewpoint of economy, it is preferable to use carbon black 123, which is widely used as a rubber reinforcing additive or a resin colorant.

It has not been known so far that the carbon material 114 of the present embodiment is effective as a flame retardant by itself. On the other hand, in this embodiment, a general flame retardant for resin is not used. For example, typical flame retardants for resins include aluminum hydroxide, magnesium hydroxide, red phosphorus, ammonium phosphate, ammonium carbonate, zinc borate, molybdenum compounds, brominated monomers, brominated epoxy, brominated ethers, and brominated. Polystyrene, phosphoric acid ester, melamine cyanurate, triazine compound, guanidine compound, silicon polymer and the like are known. These are not suitable for making the heat insulating material 108 of the present embodiment flame-retardant mainly from the viewpoint of water dispersibility.

The carbon material 114 used in the present embodiment is added in advance to an aqueous raw material, and is not particularly limited as long as it is a hydrophilic functional group from the viewpoint of water dispersibility, but it is economical and dispersible. From the viewpoint, it is preferable that the aromatic carbon compound is oxidized with a hydroxyl group, a carboxyl group, a sulfonyl group or the like.

Since the oxidation-treated carbon material 114 is negatively charged and has autocovariance, it does not easily settle even when added to the raw material, and can be stored for a relatively long time. Further, the negatively charged carbon material 114 is adsorbed on the surface of the positively charged nonwoven fabric fiber 116 by electrostatic interaction when the raw material sol is impregnated into the nonwoven fabric fiber 116, and the concentration of the carbon material 114 is unevenly distributed. It is effective in forming.

The average particle size distribution of the carbon material 114 is preferably 50 to 500 nm. If the average particle size distribution is smaller than 50 nm, productivity may be inferior. If the average particle size distribution is larger than 500 nm, it will settle relatively easily in the raw material sol, and the carbon material 114 will settle and deposit in the tank and piping during mass production, resulting in unintended concentration changes and pipe clogging. Furthermore, there is a problem that the nozzle is clogged.

The amount of the carbon material 114 added is preferably 0.01 to 10.00% by weight with respect to the total weight of the heat insulating material 108. If it is less than 0.01% by weight, an effective flame retardant effect may not be obtained. If it is more than 10.00% by weight, the thermal conductivity may increase and the heat insulating property may not be effectively ensured.

The ratio (distribution) of the added carbon material 114 in each layer is approximately 51 to 99% by weight with respect to the addition amount in the two-component composite layer 102, and 1 to 49% by weight with respect to the addition amount in the three-component composite layer 103. preferable. That is, when 10% by weight of the carbon material 114 is added, 5.1 to 9.9% by weight, which corresponds to approximately 51 to 99% of the added amount of 10% by weight in the two-component composite layer 102, and the three-component composite layer 103. Then, 0.1 to 4.9% by weight, which corresponds to 1 to 49% of the addition amount of 10% by weight, is preferable.

Although the carbon material 114 used in the present embodiment has flame retardancy, if it is added too much, the thermal conductivity of the heat insulating material 108 increases because the conduction heat transfer λs of the solid increases. It is necessary to pay attention to the amount of addition and how to distribute it.

<Thickness of heat insulating material 108>
The thickness of the heat insulating material 108 is in the range of 0.03 mm to 5.0 mm. The thickness is preferably in the range of 0.05 mm to 3.0 mm. When the heat insulating material 108 is thinner than 0.03 mm, the heat insulating effect in the thickness direction is reduced. Therefore, unless a very low thermal conductivity with a thermal conductivity close to that of a vacuum is realized, heat transfer in the thickness direction from one surface to the other cannot be satisfactorily reduced. When it is thicker than 0.05 mm, the heat insulating effect in the thickness direction can be secured.

On the other hand, if the heat insulating material 108 is thicker than 3.0 mm, it becomes difficult to incorporate it into a device that has become thinner and smaller in recent years.

<Content rate of silica xerogel 115 in heat insulating material 108>
The thickness of the heat insulating material 108 is in the range of 0.03 mm to 5.0 mm, preferably 0.05 mm to 3.0 mm. The optimum range of the ratio of the weight of the silica xerogel 115 to the total weight varies depending on the basis weight, bulk density, and thickness of the non-woven fabric fiber 116.

Therefore, it may be at least 40% by weight or more. If it is less than 40% by weight, it becomes difficult to reduce the thermal conductivity. Further, it may be 80% by weight or less. If it is higher than 80% by weight, the thermal conductivity is lowered, but the flexibility and strength are insufficient, and the silica xerogel 115 may fall off due to repeated use.

<Metsuke of non-woven fabric fiber 116>
As the basis weight of the nonwoven fabric fiber 116, 5 to 500 g / m ² is used. The numerical values will also be described in the following examples. The basis weight is the weight per unit area.

<Bulk density of non-woven fabric fiber 116>
The bulk density of the non-woven fabric fiber 116 is preferably in the range of 100 to 500 kg / m ³ from the viewpoint of increasing the content of silica xerogel 115 in the heat insulating material 108 and further reducing the thermal conductivity.

In order to form the non-woven fabric fiber 116 with mechanical strength as a continuum, a bulk density of at least 100 kg / m ³ is required. Further, when the bulk density of the nonwoven fabric fiber 116 is larger than 500 kg / m ³ , the space volume in the nonwoven fabric fiber 116 is reduced, so that the silica xerogel 115 that can be filled is relatively reduced and the thermal conductivity is increased. The numerical values will also be described in the following examples.

<Material of non-woven fabric fiber 116>
As the material of the non-woven fiber 116, from the viewpoint of non-combustibility, aramid fiber, polyimide fiber, novoloid fiber, glass fiber, polyphenylene sulfide (PPS) fiber, acrylic oxide fiber, graphite fiber having a limiting oxygen index (LOI) of 25 or more. , It is preferable that it contains at least one type of carbon fiber.

<Flame-retardant mechanism of heat insulating material 108>
The flame retardant mechanism will be described below. The insulation 108 is contained in the same layer as the silica xerogel 115 and the carbon material 114. The surface of the silica particles constituting the silica xerogel 115 is organically modified and exhibits hydrophobicity. However, when heated at a high temperature of 300 ° C. or higher, this organic modifying group is thermally decomposed, and trimethylsilanol and the like are desorbed in large quantities as a flammable gas. This flammable gas may act as a combustion improver.

For example, in the glass paper made of C glass, the base material itself does not burn, but when silica xerogel 115 (800 m ² / g or more) having a large specific surface area is compounded with this glass paper, a large amount of silica xerogel 115 is generated. In some cases, the flammable gas ignites and the glass paper made of C glass burns. C glass has lower heat resistance than E glass, and although it depends on the basis weight, it shrinks and deforms when heated to 750 ° C. or higher.

On the other hand, in the heat insulating material 108 of the embodiment, a large amount of carbon dioxide is generated and released by the reaction between oxygen in the atmosphere and the carbon material 114 in an atmospheric atmosphere at a high temperature of 300 ° C. or higher. This prevents the combustible gas desorbed from the silica xerogel 115 from burning.

<Manufacturing method of the composite layer 103 of three components>
FIG. 5 shows an outline of a method for manufacturing the three-component composite layer 103.

(1) Sol preparation 1 part by weight of self-dispersive carbon black CB (Aqua-Black (R) 162, solid content concentration 19.2% by weight of Tokai Carbon Co., Ltd.) in a water glass aqueous solution (Toso Sangyo Co., Ltd.) Addition to prepare a water glass aqueous solution dispersion of carbon black CB (SiO ₂ concentration 6%, carbon black CB 1.3%). To this dispersion, 3.6 parts by weight of concentrated hydrochloric acid as an acid catalyst is added and stirred to prepare a sol solution. However, the raw material species for silica is not limited to water glass, and alkoxysilane or high molar sodium silicate may be used.

The types of acids used include hydrochloric acid, nitric acid, sulfuric acid, hydrofluoric acid, sulfite, phosphoric acid, phobic acid, hypophobic acid, chloric acid, chloric acid, hypochlorous acid and other inorganic acids, and acidic phosphoric acid. Examples thereof include acidic phosphates such as aluminum, acidic magnesium phosphate and zinc acidic phosphate, and organic acids such as acetic acid, propionic acid, oxalic acid, succinic acid, citric acid, malic acid, adipic acid and azelaic acid. The type of acid catalyst used is not limited, but hydrochloric acid is preferable from the viewpoint of gel skeleton strength and hydrophobicity of the obtained silica xerogel 115.

The above acid catalyst is added to the aqueous glass solution to gel the sol solution prepared. The gelation of the sol is preferably carried out in a closed container so that the liquid solvent does not volatilize.

When an acid is added to a high molar silicic acid aqueous solution to gel it, the pH value at that time is preferably 4.0 to 8.0. If the pH is less than 4.0 or greater than 8.0, the high molar silicic acid aqueous solution may not gel depending on the temperature at that time.

(2) Impregnation of non-woven fabric A sol solution is poured into a non-woven fabric fiber 116 (material is glass paper, thickness is 600 um, grain is 110 g / m ² , and size is 12 cm square) and impregnated. The impregnation amount of the sol solution is used in excess of the theoretical space volume in the nonwoven fiber 116 (> 100%). The theoretical space volume in the nonwoven fabric fiber 116 is calculated from the bulk density of the nonwoven fabric fiber 116. The material, thickness, and bulk density of the nonwoven fabric fiber are not limited to the above as described above. Further, as the impregnation method, a method of immersing the nonwoven fabric roll in the sol solution for each roll or a method of applying the sol solution from the dispenser or the spray nozzle while feeding the nonwoven fabric fibers 116 at a constant speed by Roll to Roll may be used. However, from the viewpoint of productivity, the Roll to Roll method is preferable.

The cross-sectional view of FIG. 6A shows a process of dripping and impregnating the raw material sol 124 in which the carbon material 114 is dispersed in the nonwoven fabric fiber 116. The molecular surface of the carbon material 114 is negatively charged. The non-woven fabric fiber 116 is preferably positively charged in order to adsorb the carbon material 114 on the surface of the non-woven fabric fiber 116 and form a structure in which the carbon material 114 is unevenly distributed at high density on one side or both sides of the heat insulating material 108. .. By using the positively charged nonwoven fabric fiber 116, the carbon material 114 is adsorbed on the surface of the nonwoven fabric fiber 116 by electrostatic interaction, and it is effective to form a structure in which the concentration of the carbon material 114 is unevenly distributed. As a result, the non-woven fabric fiber 116 impregnated with the sol solution shown in the cross-sectional view of FIG. 6B is formed.

(3) Film sandwiching The non-woven fabric fiber 116 impregnated with the sol solution is sandwiched between PP films (thickness 50 um × 2, size B6) and left at room temperature 23 ° C. for about 3 minutes to gel the sol. The material and thickness of the film sandwiching the impregnated non-woven fabric in the gelation standby, thickness regulation, and curing process are not limited to the above. Since the film material requires heating in the curing process, the maximum operating temperature of polypropylene (PP), polyethylene terephthalate (PET), etc. is 100 ° C or higher, and the coefficient of linear thermal expansion is 100 (× 10- ⁾ . A resin material having a temperature of ⁶ / ° C. or less is preferable.

(4) Thickness regulation After confirming gelation, pass the non-woven fabric fiber 116 impregnated with the film through a biaxial roll with a gap set to 1.000 mm (including film thickness), and squeeze out excess gel from the non-woven fabric fiber 116 to increase the thickness. Regulate with the aim of 1.0 mm. The method for regulating the thickness is not limited to the above, and the thickness may be regulated by a method such as a squeegee or a press.

(5) Film peeling After removing the curing container from the constant temperature bath and allowing it to cool at room temperature, the cured sample is taken out and the film is peeled off.

(6) Hydrophobization 1 (hydrochloric acid dipping step)
After immersing the gel sheet in hydrochloric acid (specified in 4 to 12), leave it at room temperature of 23 ° C. for 5 minutes or more to incorporate hydrochloric acid into the gel sheet.

(7) Hydrophobization 2 (siloxane treatment step)
The gel sheet is, for example, immersed in a mixed solution of octamethyltrisiloxane as a silylating agent and 2-propanol (IPA) as an alcohol, and placed in a constant temperature bath at 55 ° C. for reaction for 2 hours. When the trimethylsiloxane bond begins to be formed, hydrochloric acid water is discharged from the gel sheet and separated into two liquids (siloxane in the upper layer, hydrochloric acid water in the lower layer, 2-propanol).

(8) Drying The gel sheet is transferred to a constant temperature bath at 150 ° C. and dried for 2 hours.

As described above, an example of manufacturing the three-component composite layer 103 has been shown according to FIG. 6, but the present invention is not limited thereto.

<Manufacturing of heat insulating material 108>
When the heat insulating material 108 is manufactured, the heat insulating material 108 can be manufactured according to the type and amount of the carbon material 114 to be added in (1) sol preparation in the above <method for manufacturing the composite layer 103 of three components>. That is, when the three-component composite layer 103 is manufactured, the two-component composite layer 102 or the one-component single layer 101 can also be manufactured.

Due to the interaction between the carbon material 114 whose molecular surface is negatively charged and the surface of the non-woven fabric fiber 116 which is positively charged, a two-component composite layer 102 containing a high concentration carbon material 114 is formed on the impregnated side. On the opposite side is a one-component single layer 101 that does not contain the carbon material 114. As a result, the heat insulating material 108 of FIG. 1 (a) is produced.

On the other hand, when the carbon material 114 is increased, the two-component composite layer 102 is formed on both sides of the two-component composite layer 102. Although it depends on the carbon type, when the addition concentration of the carbon material 114 is as small as less than 1% by weight, the structure of FIG. 1 (a) is formed, and when the addition concentration of the carbon material 114 is 1% by weight or more, FIG. 1 (b). ) Structure is created.

Hereinafter, the present embodiment will be described based on the examples. However, this embodiment is not limited to the following examples. All reactions were carried out under the atmosphere.

<Evaluation>
In the examples, the heat insulating material 108 when the carbon material 114 was added and the heat insulating material 110 to which the carbon material 114 was not added were produced, and the following measurements were made for each.

<Measurement of thermal conductivity>
For the thermal conductivity measurement, a heat flow meter HFM 436 Lamda (manufactured by NETZCH) and TIM tester (manufactured by Anysys Tech) were used.

<UL94 vertical combustion test>
In addition, a UL94 vertical combustion test was conducted to evaluate the flame retardancy of the heat insulating material 108 and the heat insulating material 110. What is UL? UNDERWRITERS LABORATORIES INC. In the United States. It is a safety standard for electrical equipment established and approved by the company. It is even said that getting UL certification is a sign of safety. UL is applied to products in various fields such as electric products, fire prevention equipment, plastic materials, lithium batteries, and electric vehicle-related equipment. The UL94 category is "Plastic Combustibility Tests for Equipment and Appliance Parts" and there are two types: horizontal and vertical combustion tests. In the UL94 vertical combustion test conducted this time, a sample of a certain size is grasped vertically, the tip is burned with a burner for a predetermined time, and pass / fail is determined by the residual flame time.

<Differential Scanning Calorimetry (DSC)>
A differential scanning calorimetry (DSC) was performed between the silica xerogel 115 containing the carbon material 114 present on the surface layer of the heat insulating material 108 and the silica xerogel 115 existing on the surface layer of the heat insulating material 110, and the thermal decomposition temperatures of the organic modifying groups were compared. did.

<Cone calorie meter heat generation test>
The cone calorie meter heat generation test is applied to the fire protection material test stipulated by the Building Standards Law. It is widely recognized internationally as a test method for handling material combustion. This method can measure various combustion parameters such as heat generation rate and combustion time, and can quantify the combustion phenomenon.

In the test, a 10 cm square sample is burned using an electric spark as an ignition source while applying radiant heat of 50 kW / m ² . The heat generation rate over time, the total heat generation amount from the start to the end of combustion, the combustion time, etc. are calculated and evaluated.

Specifically, in the technical standards for non-combustible materials specified in the Building Standards Law Construction Ordinance, a heat generation test was carried out using a cone calorie meter tester compliant with ISO5660-1ISO5660, ASTM E1354, and NFPA 264A.

The measurement principle of the cone calorie meter heat generation test will be explained. In this test, the heat generation rate and heat generation amount are determined by a method called "oxygen consumption method". The calorific value generated by combustion varies greatly from substance to substance in terms of the weight of the substance to be burned. However, the calorific value generated by combustion utilizes the fact that it shows a substantially constant value regardless of the type of substance in terms of the weight of oxygen consumed (13.1 MJ per 1 kg of oxygen). That is, the combustion phenomenon is quantified by accurately measuring the amount of oxygen consumed during combustion.

The detailed conditions of each example and comparative example will be described below. Further, the conditions and the evaluation results are shown in FIG. In FIG. 7, GO is Graphene Oxide, CB is Carbon Black, SWCNT is Single Walled Carbon Nanotube, PEDOT is PSS, and Poly (3,4-ethylenedioxythione) -poly.

<Passing criteria>
(1) Thermal conductivity evaluation The thermal conductivity of the heat insulating material 108 was 0.024 W / mK or less. The thermal conductivity of static air at room temperature is said to be about 0.026 W / mK. Therefore, in order to effectively cut off the heat flow, it is necessary to set the thermal conductivity of the heat insulating material 108 to be smaller than that of the static air.

Therefore, the acceptance criteria for the thermal conductivity of the heat insulating material 108 is 0.024 W / mK or less, which is about 10% lower than the thermal conductivity of the static air. If it is larger than 0.024 W / mK, it is not so different from the thermal conductivity of static air, and therefore the superiority to air insulation is impaired.

(2) Decomposition temperature of organic modifying group The thermal decomposition temperature of 400 ° C or higher was accepted. When the thermal decomposition temperature of the organic modifying group is less than 400 ° C., a large amount of trimethylsilanol, which is a flammable gas, is likely to be generated at 400 ° C. or lower, which causes ignition.

(3) Flame retardancy evaluation V0 was passed in the UL94 vertical combustion test. In the UL94 combustion test, the strictest V0 was passed, and V1, V2 and flammable were rejected. The test method is common to all three types of V0, V1 and V2, and the flame of the gas burner is brought into contact with the lower end of the vertically held sample for 10 seconds. If the combustion stops within 30 seconds, indirect flame is applied for another 10 seconds. The judgment criteria of V0, V1 and V2 are shown.

(criterion)
V-0: No sample continues to burn for more than 10 seconds after any flame contact. The total burning time for 10 flame contact with 5 samples does not exceed 50 seconds. There is no sample that burns to the position of the fixing clamp. There is no sample to drop the burning particles that ignite the cotton wool placed below the sample. There is no sample that continues to glow for more than 30 seconds after the second flame contact. The above conditions must be met.

V-1: There is no sample that continues to burn for 30 seconds or more after any flame contact. The total burning time for 10 flame contact with 5 samples does not exceed 250 seconds. There is no sample that burns to the position of the fixing clamp. There is no sample to drop the burning particles that ignite the cotton wool placed below the sample. There is no sample that continues to glow for more than 60 seconds after the second flame contact. The above conditions must be met.

V-2: There is no sample that continues to burn for 30 seconds or more after any flame contact. For 5 samples. The total burning time for 10 flame contact does not exceed 250 seconds. There is no sample that burns to the position of the fixing clamp. Ignite the cotton wool placed under the sample. Dropping of burning particles is allowed. There is no sample that continues to glow for more than 60 seconds after the second flame contact. The above conditions must be met.
(4) Cone calorie meter heat generation test In the cone calorie meter heat generation test, in the non-combustible material test (20 minutes), the burning time is 10 seconds or less and the maximum heat generation rate (HRR; Heat Release Rate) is 15 kW / m2. The following were accepted.

(5) Comprehensive evaluation The conditions that satisfy all of them were accepted as the comprehensive evaluation.

<Overall>
Examples 1 to 8 are the structures of the heat insulating material 108 of FIG. 1 (a) or FIG. 1 (b). Comparative Examples 1 and 2 have a conventional one-layer heat insulating material structure. The conventional heat insulating material is only one layer of the non-woven fabric fiber 116 and the silica xerogel 115. Comparative Example 3 is only the non-woven fabric fiber 116. Comparative Example 3 is a heat insulating material in which the non-woven fabric fiber 116 is made of glass paper. The following concentration is% by weight.

<Example 1>
Self-dispersive graphene oxide (Sigma-Aldrich, 4 mg / ml in _H2O ) and water are added to water glass (Toso Sangyo Co., Ltd.) to add raw materials (SiO ₂ concentration 6%, graphene oxide GO concentration 0. 1%) was prepared. To 20.5 g of this dispersion, 3.6 parts by weight (0.74 g) of concentrated hydrochloric acid was added as an acid catalyst and stirred to prepare a sol solution.

Next, the nonwoven fabric fiber 116 was impregnated with the sol solution by pouring the sol solution into the nonwoven fabric fiber 116 (material; glass paper, thickness specification 600 um, grain 100 g / m ² , dimension 12 cm square). The non-woven fabric fiber 116 impregnated with the sol solution was sandwiched between PP films (thickness 50 um × 2 sheets) and left at room temperature of 23 ° C. for 3 minutes to gel the sol. After confirming gelation, pass the non-woven fabric fiber 116 impregnated with the film through a biaxial roll with a gap set to 1.00 mm (including film thickness), squeeze out excess gel from the non-woven fabric fiber 116, and regulate with the aim of thickness 1.00 mm. did.

Next, the film was peeled off, the gel sheet was immersed in hydrochloric acid No. 6 and then left at room temperature of 23 ° C. for 5 minutes to allow hydrochloric acid to be incorporated into the gel sheet. Then, the gel sheet was immersed in a mixed solution of octamethyltrisiloxane as a silylating agent and 2-propanol (IPA), and placed in a constant temperature bath at 55 ° C. for 2 hours reaction. When the trimethylsiloxane bond began to be formed, hydrochloric acid water was discharged from the gel sheet, and the two liquids were separated (siloxane in the upper layer, hydrochloric acid water in the lower layer, 2-pronol). The gel sheet was transferred to a constant temperature bath set at 150 ° C. and dried in an air atmosphere for 2 hours to obtain a sheet.

As a result, a heat insulating material 108 having an average thickness of 0.89 mm and a thermal conductivity of 0.019 W / mK was obtained. The filling factor of silica xerogel 115 at this time was 45.5% by weight. It was V0 in the UL94 vertical combustion test. Further, as a result of DSC measurement, the thermal decomposition temperature (exothermic peak) of the organic modifying group was 550 ° C. or higher, which was shifted to the higher temperature side by 190 ° C. or higher than when the carbon material 114 was not added. In the corn calorie test, in the non-combustible material test for 20 minutes, the burning time was 0 seconds and the maximum heat generation rate was 2.5 kW / m ² .

<Example 2>
Self-dispersive graphene oxide (Sigma-Aldrich, 4 mg / ml in _H2O ) and water are added to an aqueous solution of water glass (Toso Sangyo Co., Ltd.) to add raw materials (SiO ₂ concentration 6%, graphene oxide GO concentration 0). .5%) was prepared. Sheets were prepared under the same process conditions as in Example 1 except that the graphene oxide concentration was increased to 0.5%.

As a result, a heat insulating material 108 having an average thickness of 0.88 mm and a thermal conductivity of 0.020 W / mK was obtained. The filling factor of silica xerogel 115 at this time was 44.6% by weight. It was V0 in the UL94 vertical combustion test. Further, as a result of DSC measurement, the thermal decomposition temperature (exothermic peak) of the organic modifying group was 550 ° C. or higher, which was shifted to the higher temperature side by 190 ° C. or higher than when the carbon material 114 was not added. In the corn calorie test, in the non-combustible material test for 20 minutes, the burning time was 0 seconds and the maximum heat generation rate was 1.36 kW / m ² .

<Example 3>
Self-dispersive carbon black (Tokai Carbon, Aqua black 162 19.2 wt% in H2 O) and water _are added as carbon material 114 to an aqueous water glass solution (Toso Sangyo Co., Ltd.) to add raw materials (SiO2 concentration 6%). , Carbon black CB concentration 0.1%) was prepared. To 20.5 g of this dispersion, 3.6 parts by weight (0.74 g) of concentrated hydrochloric acid was added as an acid catalyst and stirred to prepare a sol solution. A sheet was prepared under the same process conditions as in Example 1 except that the carbon material was changed to carbon black.

As a result, a heat insulating material 108 having an average thickness of 0.88 mm and a thermal conductivity of 0.019 W / mK was obtained. The filling factor of silica xerogel 115 at this time was 45.9% by weight. It was V0 in the UL94 vertical combustion test. Further, as a result of DSC measurement, the thermal decomposition temperature (exothermic peak) of the organic modifying group was 550 ° C. or higher, which was shifted to the higher temperature side by 190 ° C. or higher than when the carbon material 114 was not added. In the corn calorie test, in the non-combustible material test for 20 minutes, the burning time was 0 seconds and the maximum heat generation rate was 1.33 kW / m ² .

<Example 4>
Self-dispersive carbon black (Tokai Carbon, Aqua black 162 19.2 wt% in H2 O) and water _are added as carbon material 114 to an aqueous water glass solution (Toso Sangyo Co., Ltd.) to add raw materials (SiO2 concentration 6%). , Carbon black CB concentration 0.5%) was prepared. To 20.5 g of this dispersion, 3.6 parts by weight (0.74 g) of concentrated hydrochloric acid was added as an acid catalyst and stirred to prepare a sol solution. Sheets were prepared under the same process conditions as in Example 3 except that the concentration of carbon black was increased to 0.5%.

As a result, a heat insulating material 108 having an average thickness of 0.87 mm and a thermal conductivity of 0.018 W / mK was obtained. The filling factor of silica xerogel 115 at this time was 45.7% by weight. It was V0 in the UL94 vertical combustion test. Further, as a result of DSC measurement, the thermal decomposition temperature (exothermic peak) of the organic modifying group was 550 ° C. or higher, which was shifted to the higher temperature side by 190 ° C. or higher than when the carbon material 114 was not added. In the corn calorie test, in the non-combustible material test for 20 minutes, the burning time was 0 seconds and the maximum heat generation rate was 1.10 kW / m ² .

FIG. 8 is an observation image of a flame-retardant heat insulating material (composite of a non-woven fabric fiber 116 made of glass paper and silica xerogel 115) produced in Example 4 and Comparative Example 1 with a scanning electron microscope. In Example 4, it was confirmed that the carbon material 114 was adsorbed on the fiber surface.

<Example 5>
To a water glass aqueous solution (Toso Sangyo Co., Ltd.), carbon nanotube SWCNT (Sigma-Aldrich), which is PEG-modified as a carbon material 114 to improve dispersibility, and water are added, and the raw materials (SiO ₂ concentration 6%, SWCNT) are added. Concentration 0.1%) was prepared. To 20.5 g of this dispersion, 3.6 parts by weight (0.74 g) of concentrated hydrochloric acid was added as an acid catalyst and stirred to prepare a sol solution. Sheets were prepared under the same process conditions as in Example 1 except that the carbon material was changed to SWCNT.
As a result, a heat insulating material 108 having an average thickness of 0.85 mm and a thermal conductivity of 0.018 W / mK was obtained. The filling factor of silica xerogel 115 at this time was 45.5% by weight. It was V0 in the UL94 vertical combustion test. Further, as a result of DSC measurement, the thermal decomposition temperature (exothermic peak) of the organic modifying group was 550 ° C. or higher, which was shifted to the higher temperature side by 190 ° C. or higher than when the carbon material 114 was not added. In the corn calorie test, in the non-combustible material test for 20 minutes, the burning time was 10 seconds and the maximum heat generation rate was 14.06 kW / m ² .

<Example 6>
A carbon nanotube SWCNT (Sigma-Aldrich) and water, which have been PEG-modified as a carbon material 114 to improve dispersibility, are added to an aqueous water glass solution (Tosoh Sangyo Co., Ltd.) to add raw materials (SiO2 concentration 6%, SWCNT concentration). 0.5%) was prepared. To 20.5 g of this dispersion, 3.6 parts by weight (0.74 g) of concentrated hydrochloric acid was added as an acid catalyst and stirred to prepare a sol solution. Sheets were prepared under the same process conditions as in Example 5 except that the concentration of SWCNT was increased.

As a result, a heat insulating material 108 having an average thickness of 0.86 mm and a thermal conductivity of 0.018 W / mK was obtained. The filling factor of silica xerogel 115 at this time was 45.6% by weight. It was V0 in the UL94 vertical combustion test. Further, as a result of DSC measurement, the thermal decomposition temperature (exothermic peak) of the organic modifying group was 550 ° C. or higher, which was shifted to the higher temperature side by 190 ° C. or higher than when the carbon material 114 was not added. In the corn calorie test, in the non-combustible material test for 20 minutes, the burning time was 10 seconds and the maximum heat generation rate was 13.02 kW / m ² .

<Example 7>
Poly (3,4-ethylenedioxythiophene) / polysulfonic acid (PEDOT: PSS) (SEPLEGYDA AS-Q09, Shin-Etsu Polymer) and water are added to the water glass aqueous solution (Toso Sangyo Co., Ltd.) as the carbon material 114. , Raw materials (SiO2 concentration 6%, SWCNT concentration 0.5%) were prepared. To 20.5 g of this dispersion, 3.6 parts by weight (0.74 g) of concentrated hydrochloric acid was added as an acid catalyst and stirred to prepare a sol solution. Sheets were prepared under the same process conditions as in Example 1 except that the carbon material was changed to PEDOT: PSS.

As a result, a heat insulating material 108 having an average thickness of 0.86 mm and a thermal conductivity of 0.018 W / mK was obtained. The filling factor of silica xerogel 115 at this time was 45.9% by weight. It was V0 in the UL94 vertical combustion test. Further, as a result of DSC measurement, the thermal decomposition temperature (exothermic peak) of the organic modifying group was 550 ° C. or higher, which was shifted to the higher temperature side by 190 ° C. or higher than when the carbon material 114 was not added. In the corn calorie test, in the non-combustible material test for 20 minutes, the burning time was 0 seconds and the maximum heat generation rate was 1.31 kW / m ² .

<Example 8>
1 part by weight of self-dispersive carbon black (Tokai Carbon, Aqua black 162 19.2 wt% in _H2O ) was added to a high molar sodium silicate aqueous solution (Tokai Sangyo Co., Ltd.) to make a raw material (SiO2 concentration 14%, Carbon black CB concentration 1.3%) was prepared. To 20.5 g of this dispersion, 1.6 parts by weight (0.33 g) of concentrated hydrochloric acid was added as an acid catalyst and stirred to prepare a sol solution.

Impregnation and thickness regulation were performed under the same conditions as in Example 1, and the gel was heated at a temperature of 90 ° C. for 5 minutes in order to strengthen the gel skeleton. From peeling the film to drying, the process conditions were the same as those in Example 1 except that the hydrochloric acid concentration was changed to No. 12.

As a result, a heat insulating material 108 having an average thickness of 1.3 mm and a thermal conductivity of 0.018 W / mK was obtained. The filling factor of silica xerogel 115 at this time was 67.6% by weight. It was V0 in the UL94 vertical combustion test. Further, as a result of DSC measurement, the thermal decomposition temperature (exothermic peak) of the organic modifying group was 550 ° C. or higher, which was shifted to the higher temperature side by 190 ° C. or higher than when the carbon material 114 was not added. In the corn calorie test, in the non-combustible material test for 20 minutes, the burning time was 14.7 seconds and the maximum heat generation rate was 10.94 kW / m ² .

<Comparative Example 1>
Sheets were prepared under the same process conditions as in Example 1 except that self-dispersing graphene oxide was not added to the raw water glass aqueous solution.

As a result, a heat insulating material 107 having an average thickness of 0.86 mm and a thermal conductivity of 0.019 W / mK was obtained. The filling factor of silica xerogel 115 at this time was 45.4% by weight. In the UL94 vertical combustion test, it burned and was not V0. As a result of DSC measurement, the thermal decomposition temperature (exothermic peak) of the organic modifying group was as low as 360 ° C. It is probable that the reason why the combustion was carried out in the combustion test was that a large amount of combustible gas was generated near 360 ° C and ignited. In the corn calorie test, in the non-combustible material test for 20 minutes, the burning time was 12.7 seconds and the maximum heat generation rate was 16.39 kW / m ² . The overall evaluation was unsuccessful.

<Comparative Example 2>
A heat insulating sheet was prepared under the same process conditions as in Example 8 except that the carbon material 114 was not added to the high molar sodium silicate aqueous solution (Toso Sangyo Co., Ltd.).

As a result, a heat insulating material 107 having an average thickness of 1.03 mm and a thermal conductivity of 0.020 W / mK was obtained. The filling factor of silica xerogel 115 at this time was 63.0% by weight. In the UL94 vertical combustion test, it burned and was not V0. As a result of DSC measurement, the thermal decomposition temperature (exothermic peak) of the organic modifying group was as low as 380 ° C. It is probable that the reason why the combustion was carried out in the combustion test was that a large amount of combustible gas was generated near 380 ° C and ignited. In the corn calorie test, in the non-combustible material test for 20 minutes, the burning time was 24.8 seconds and the maximum heat generation rate was 28.69 kW / m ² . The overall evaluation was unsuccessful.

<Comparative Example 3>
The thermal conductivity was 0.033 W / mK as a result of measuring the thermal conductivity of the non-woven fabric fiber 116 having a thickness of 0.600 mm, a grain size of 100 g / m ² , and a material of glass paper without compounding silica xerogel 115. In the UL94 vertical combustion test, it did not burn and was V0. However, since the thermal conductivity is larger than 0.024 W / mK, it failed as a comprehensive evaluation.

<Result>
(1) Comparison between Example 4 and Comparative Example 1 FIG. 8 shows a scanning type of a heat insulating material (composite of a non-woven fabric fiber 116 made of glass paper and silica xerogel 115) produced in Example 4 and Comparative Example 1. It is an observation image of an electron microscope. In Example 1, carbon black particles are adsorbed on the surface of the non-woven fabric fiber 116. On the other hand, in Comparative Example 1, the carbon material 114 adsorbed on the surface of the non-woven fabric fiber 116 does not exist.

(2) Overall In Examples 1 to 8, the thermal decomposition temperature was shifted to 400 ° C. or higher by producing the heat insulating material 108 in which the carbon material 114 was unevenly distributed on the surface, and the UL94 vertical combustion test was performed at V0. At the same time, it was found that the thermal conductivity was as low as 0.024 W / mK or less.

In addition, a non-combustible material test (20 minutes) was carried out for each sample in the cone calorie meter heat generation test.

As a result, the heat insulating materials of Comparative Examples 1 and 2 to which no carbon material is added have a maximum heat generation rate (HRR; Heat Release Rate) of 15 kW / m ² or more, or a combustion time of 15 seconds or more. It was not compatible. However, in Examples 1 to 8 in which 0.1% by weight or more of the carbon material was added, the maximum heat generation rate (HRR; Heat Release Rate) was 15 kW / m ² or less and the combustion time was 15 seconds or less, both of which were satisfied. At this time, carbon black, graphene oxide, carbon nanotubes in a carbon layer, and PEDOT: PSS are effective as the type of carbon material 114, and it has been found that the addition amount thereof is preferably 0.1 to 1.3% by weight. ..
(as a whole)
Although the structure of FIGS. 1 (a) and 1 (b) has been described, the present invention is not limited to this structure. That is, the effect as a heat insulating material and the above-mentioned problems can be solved only by the composite layer 103 having three components.

The heat insulating material of the present embodiment is widely used because it can sufficiently exert a heat insulating effect even in a narrow space in an electronic device, an in-vehicle device, or an industrial device. It is applied to all heat-related products such as information devices, mobile devices, displays, and electrical components.

101 1-component single layer 102 2-component composite layer 103 3-component composite layer 107 Insulation 108 Insulation 110 Insulation 111 Silica primary particles 112 Silica secondary particles 113 Pore 114 Carbon material 115 Silica xerogel 116 Non-woven fiber 118 Fulleren 119 Graphen 120 Carbon Nanotube 123 Carbon Black 124 Raw Material Sol

Claims (9)

Silica xerogel and
With carbon material,
Containing a non-woven fiber that holds the silica xerogel and the carbon material.
In the cone calorie meter heat generation test, it is a heat insulating material having a burning time of 15 seconds or less and a maximum heat generation rate of 15 kW / m ² or less.
The carbon material is a carbon material containing at least one aromatic fused ring, and is a carbon material that reacts with O ₂ in the atmosphere at a high temperature of 300 ° C. or higher to generate CO ₂ .
The carbon material is 0.01 to 10.00% by weight based on the total weight of the heat insulating material.
A heat insulating material which is one layer of a three-component composite layer containing the silica xerogel, the carbon material, and the non-woven fabric fiber. The heat insulating material according to claim 1, wherein the carbon material is self-dispersed carbon that has been oxidized. The heat insulating material according to claim 1 or 2, wherein in the cone calorie meter heat generation test, the burning time is 14.7 seconds or less and the maximum heat generation rate is 14.06 kW / m ² or less. The heat insulating material according to any one of claims 1 to 3, wherein the carbon material is carbon black. The heat insulating material according to any one of claims 1 to 4, wherein the carbon material contains at least one type of fused ring having aromaticity. The heat insulating material according to any one of claims 1 to 5, wherein the carbon material has an average particle size of 50 to 500 nm. The silica xerogel, the carbon material, and the heat insulating material of the composite layer of the three components composed of the non-woven fabric fiber,
A two-component composite layer containing the silica xerogel and the carbon material without containing the non-woven fabric fibers arranged on one surface of the three-component composite layer.
A single layer containing silica xerogel, which is arranged on the other surface of the composite layer of the three components,
The heat insulating material according to any one of claims 1 to 6. The silica xerogel, the carbon material, and the heat insulating material of the composite layer of the three components composed of the non-woven fabric fiber,
The heat insulating according to any one of claims 1 to 6 , which does not include the non-woven fabric fibers arranged on both sides of the three-component composite layer and includes the silica xerogel and the two-component composite layer containing the carbon material. Material. A device in which the heat insulating material according to any one of claims 1 to 8 is arranged as a part of a heat insulating or cold insulating structure or between a component and a housing that generate heat.

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